Combustion device for and method of measuring flame characteristics of gases



MARKLE FoR AND METHOD OF MEASURING FLAME CHARACTERISTICS OF GASES 2Sheets-Sheet l .26 6k: 55 5 thi I o 0 xi! M m MVP 5 mm /.fl .7 J 0 W a J6J w/ w a z 0 50 W I y I iwrfiaw fl/af/kaw (YT/$7 7776 June 1942 M. G.MARKLE 4 2,235,866

COMBUSTION DEVICE FOR AND METHOD OF MEASURING FLAME CHARACTERISTICS OFGASES Filed March 9, 1959 2 Sheets-Sheet 2 Patented June 9, 1942 UNITEDSTATES PATENT OFFICE COMBUSTION DEVICE FOR AND METHOD OF MEASURING FLAMECHARACTERISTICS OF GASES 7 Claims.

The present invention relates to measuring instruments and isparticularly concerned with devices for and method of measuring andcontrolling the quantity or quality of factors affecting the flameproduced by burning a gas or a mixture of gases.

Most appliances using gas as a source of heat include a burner in Whichgas from a supply main is delivered to the burner by a controllingorifice or the like, primary air being admitted and mixed with the gasjust before it is burned. Ordinarily, the primary air, supplying oxygenfor the combustion of the gas, is drawn into the burner by theaspirating effect of the inflowing gas and the amount of air aspiratedis controlled by a sleeve or other suitable means. Each customersappliances of this nature are therefore adjusted according to the typeor characteristics of the gas normally supplied, and, once adjusted, theburner will operate satisfactorily so long as the quality, composition,etc., of the gas do not vary to any great extent.

The characteristics of the flame produced by burning a gas or a mixtureof gases, are generally dependent upon its specific gravity, B. t. u.content and composition. That is to say, these factors usually controlthe flame velocity, total heat value and proportion of radiant heat inthe flame, and if the flame is stable, the rate of combustion at theflame front is equal to the rate of flow of gas from the burner. As willbe obvious, gases of various kinds have various flame speeds andsimilarly, different gases may have different total heat values but thesame flame speed, or the same total heat values and differentproportions of radiant heat in the flame.

Various kinds of types of gas are supplied by the utilities servingvarious localities, some companies furnishing a high B. t. u. gas,around 1000 B. t. u. and other companies furnishing 10w B. t. u. gas,around 500 to 600 B. t. u. Generally, the companies that furnish a gashaving a heating value of around 800 B. t. u. provide a mixture ofnatural gas, reformed natural gas, and manufactured or coke oven gas,depending on the season and other conditions. Straight natural gas has aheat value of about 1000 B. t. u., and the reformed natural gas andmanufactured or coke oven gas each may have a heat value of about 555 B.t. u. The heat value of a gas and its burning characteristics dependupon the various constituents in the gas mixture, and these, in turn,depend to a large extent on the composition of the coal, the heattreatment, and other operations during manufacture. During certainseasons, for operating reasons, it may be necessary to provide a supplyof make-up gas, usually in the form of carbureted water gas, at about800 B. t. u., which is mixed with the ordinary 800 B. t. u. gas mixture.It may also be necessary, as when an emergency arises such as a failureof the supply of natural gas, or for other operating reasons, to supplyadditional quantities of carburetted water gas. However, the amount ofcarburetted water gas that can be added without affecting the quality ofthe gas is limited, because carburetted water gas mixed with the usualtype of gas, even though both have the same heating value, produces adifferent burning gas and when the percentage of carbureted water gas at800 B. t. u. added to the normal 800 B. t. u. gas exceeds a definitepoint, there is some danger that the operation of customers applianceswill be affected.

For example, changing the characteristics, such as specific gravity orcomposition of the gas mixture, may produce a different burning gas,and, if the characteristics should be changed so that the radiant heatemitted or flame velocity or both, is increased, the burners of thecustomers appliances may strike back, or, if the flame velocity isdecreased, the flame may lift off the port of the burner. Usually, theamount of carbureted water gas required is not all added at one time;instead, auxiliary stations are provided at several points in the systemand equipped to add a quantity of gas as may be required for theconditions in the particular 10- cality served by the station or in anemergency, as when the normal supply of natural gas is deficient orfails. The effect of adding substantial amounts or carburetted gas, aswhere necessary to supplement the normal or base gas, is to increase theflame velocity or possibly change other characteristics of the gassupplied to the customer, and to compensate for such additions it may benecessary to adjust the flame velocity of the gas mixture by adding asubstance which will retard the flame velocity, in order to supply a gasto the customer which has its flame velocity adjusted so as to operatesatisfactorily in the customers appliances. Under other conditions itmay be desired to add an accelerant.

It was therefore recognized that some accurate and dependable way ofsecuring a measurement or indication, preferably continuous, of thosechanges in a gas mixture that effect its flame or characteristics inburning would be desirable, whereby appropriate adjustments may be madeby the operating unit so as to maintain a supply of gas in the customerslines which will not vary in those characteristics which affect burningto an extent sufficient to interfere with the proper operation of thecustomers appliances.

In solving the problem of securing a continuous measurement orindication of the type, composition, characteristics, etc., of the gassupplied to the customer, it was found that apparatus capable ofmeasuring, for example, only the heating value of the gas, apparatus formeasuring its specific gravity, or other apparatus responsive only to asingle factor or characteristic of the gas would not be satisfactory.For example, the ordinarily skilled operator of a gas plant can producea gas having substantially constant heating value and also substantiallyconstant specific gravity, yet the particular composition of the gas maybe such that its flame characteristics Would be considerably differentthan another gas of slightly difierent composition but giving the sameheating value, or specific gravity, or both. In these cases, therefore,devices responsive to only a single factor, such as specific gravity orheating value, would not respond to a change in the composition of thegas affecting its burning characteristics, and hence such devices wouldnot be useful in detecting changes in the gas supplied to 'a customerthat might be such that the burners of the customers appliances wouldstrike back or otherwise operate inefficiently, if at all.

I have discovered that with any given burner operating with any givengas, a given point on the burner itself will reach a definitetemperature and that, with other conditions remaining constant, a changein the type of gas burned will cause a definite temperature change atthe aforesaid given point on the burner. As presently understood, Ibelieve that this correspondence of temperature change at some point 'onthe burner to changes in the gas burned is due to the fact that thetemperature of the given point on the burner is responsive to any of thecharacteristics of the gas that affects its burning qualities. Forexample, if the characteristics of a gas mixture should change so thatthere would be an increase in the flame velocity of the gas, assumingsuch other factors as temperature, pressure, and the like remain thesame, the increase in the flame velocity of the'gas mixture would resultin the flame front occupying a position closer to the burner, thereforethe given point on the latter would reach a higher temperature thanwould otherwise be the'case. Further, a change in the composition of thegas, which would produce an increase in the amount of radiant heatemitted by the gas flame would, likewise, result in a temperature riseat the given point on the burner, since the burner is subjected to theradiant heat rays from the gas flame. Such a change in the radiant heatmay be produced by a change in the total heat value of the gas, or bychange in the type of gas, since two gases having the same total heatvalue may emit different proportions of the total heat as radiant heat.Thus, either kind of change would result in a change in the temperatureof the given point on the burner,

, With the above in mind, the object and general nature of thisinvention is the provision of a method of and means for measuring anychange in the proportion of a gas mixture that aifects theburningcharacteristics of the gas. Preferably, a continuous measurement isproduced so as to afford the operating department an opportunity to makeany necessary adjustment in the plant and correct the gas mixture beingsupplied before the customers appliances are affected. Also, it is afeature of this invention to provide an arrangement wherein suchadjustments may be made automatically, if desired.

More specifically, it is a feature of this invention to provide a testor control burner, which is supplied with a continuous sample of the gasthat is furnished to the customers and provided with means for measuringthe temperature at the tip or other convenient fixed location on theburner, and it is a further feature of this invention to provide acompensated temperature measurement, preferably by means of twothermocouples differentially connected, one arranged to respond to thetemperature of the tip of the burner and the other disposed in the gasmixture supplied to the burner, whereby variations in the roomtemperature, the temperature of the primary air supplied to the burneror the temperature of the gas will be eliminated in the final reading orcontrol produced by the device.

These and other objects and advantages of the present invention will beapparent to those skilled in the art after a consideration of thefollowing detailed description, taken in conjunction with theaccompanying drawings illustrating the preferred structural embodimentsof my invention.

In the drawings:

Figure l is a View, somewhat diagrammatic, showing one form of thepresent invention, including a test or control burner and a thermocouplecircuit for indicating the difference between the temperature of theburner tip and the temperature of the gas-air stream flowing to the tip;

Figure 2 is a curve showing the uniformity in burner temperaturecorresponding to a given change in the type of gas burned;

Figure 3' is a diagrammatic view, somewhat similar to that shown inFigure 1, showing an arrangement for performing certain controloperations in response to the aforesaid temperature difference; and

Figures 4 to 9, inclusive, disclose modified forms of furnace whichmaybe employed in carrying out the principles of this invention.

Referring now more particularly to Figure l, the reference numeral Iindicates a gas burner, such as an ordinary Bunsen burner, having a base2, an inlet 3 for the gas to be adjusted or controlled, a gas orifice 4,an inlet 5 for primary air, a burner tube 6, and a tip 1. The burnertube 6 includes a metal sleeve 9 fixed at its lower end to the base 2and securely connected at its upper end to a sleeve ll] of insulation,the upper end of which receives the burner tip 1, which is preferably ofmetal or other material of desirable heat absorption qualities.

Secured to the tip I is a thermocouple l5, and disposed within the tube6 is a second thermocouple H5. The thermocouples I5 and I6 are connecteddifferentially, that is, the polarity of one thermocouple is opposed tothe polarity of the other thermocouple. The thermocouples I5 and I6 areconnected serially, by leads I9, 20, and 2! the two latter leads beingconnected in the usual manner to an indicating galvanometer 22. Theinstrument 22 indicates any flow of current by virtue of onethermocouple being at a higher temperature than the other, and thepurpose of arranging the thermocouples l5 and I6 differentially, asmentioned above, is to eliminate any variations in readings due tochanges in the temperature of the surrounding air or in the temperatureof the gas mixture supplied to the inlet 3. An adjustable sleeve 25provided with openings 26 adapted to register with the openings iscapable of controlling the flow of primary air into the burner tube 6.

In operation, the gas mixture under test is supplied at a constantpressure to the inlet 3. The gas issues through the orifice 4 and passesupwardly through the tube 6, drawing in quantitles of primary air by anaspirating action, the amount of primary air is capable of beingadjusted by turning the adjusting sleeve 25 which is provided with theopenings 26 that, for maximum air supply, register with the inletopenings 5. As well understood, the gas from the orifice 4 and primaryair through the openings 5, 2S produce a combustible mixture which, whenignited, burns with a characteristic flame at the tip 1 of the burner.Seconda y air is supplied to the flame from the zone surrounding theburner. When the sleeve 25 is adjusted properly to supply the rightamount of air, the flame produced at the tip will have a characteristicshape which includes an inner cone or flame front 29 and a main flamebody 38.

The temperature at the tip I will be registered on the instrument 22,and the thermocouple I6, which responds to the temperature of the gasairstream flowing toward the flame front 29, will eliminate any variationdue to a change in temperature of the surrounding air or the temperatureof the gas supplied through the inlet 3, which would otherwise bereflected in an indicated change of temperature at the instrument 22.about four volumes of air to one volume of gas, and it will therefore berecognized that a temperature change in the primary air would have amarked effect upon the temperature at the tip I, first because anincrease or decrease in the temperature of the primary air would affectthe temperature of the flame tip, and second because an increase ordecrease in the temperature of the primary air would affect directly thetemperature of the tip 1, since the primary air, together with theincoming gas with which it is mixed, sweeps over the inner surface ofthe tip and cools the latter more or less, depending upon thetemperature difference. Therefore, providing the two thermocouples andconnecting them differentially, as described above, eliminates anyvariations due to a change in temperature of the surrounding air or thegas itself. Thus, the instrument 22 will indicate a temperature changewhen the characteristic of the flame produced by the burning of themixture varies in such a way that the height or shape of the flamechanges, or as the heat value or the proportion of radiant heat of theflame varies.

Experiments have shown that, with the other factors constant, thevarious heats at the burner tip I, as registered on the galvanometer arean indication of changes in the gaseous mixture burned by the burner. Itwas found, also, that with other factors constant, a change in pressureat which gas was supplied to the inlet 3 varied the range over whichgiven changes in the gas mixture were registered at the instrument 22. Ifound that when the gas mixture was supplied at a pressure equal tothree inches of water, the range of temperature change produced by givenchanges in the gas mixture was much greater than at a pressure equal tofive inches of water. It was also noted that with the ordinary Bunsenburner, one not having an insulation section such Ordinarily, a Bunsenburner consumes as H! in Figure 1, only about a 72 range in temperaturechange was indicated at the tip for gas mixtures varying fromapproximately 100% regular mixture (i. e., natural gas, reformed naturalgas, and coke oven gas, at 800 B. t. u.) to 100% carburetted water gas(800 B. t. u.) Apparently the metal of the burner tube in the ordinaryBunsen burner conducted the heat away from the thermocouple at the tipor flame end of the burner at a rate fast enough to prevent the fulleffects of the heat at the tip of the burner being registered on theinstrument 22, and therefore in order to produce a wider range, theconstruction shown in Figure 1 was adopted, including the insulatingsection ID. The function of the insulating section I0 is to prevent thisflow of heat away from the tip 1, so that the full effects of the heatgathered by the tip I would be effective to produce an indication at theinstrument 22. Incidentally, however, it was found that a tip ofapproximately half of the height of that indicated in Figure 1 produceda temperature range of approximately 300, but the registrations werequite variable, whereas the registrations produced at the instrument 22when using the tip I were consistent and uniform throughout the range ofchanges in gas mixture which produced temperature changes within the 160range.

Figure 2 shows, 'by way of illustration only, a chart 32 for the burnerof Figure 1, indicating the consistent correspondence of tip temperaturechanges with uniform changes in the gas mixture. The line 33 indicatesthe different temperatures indicated when the composition of the gasburned varied from regular mixture to 100% carburetted water gas, asmentioned above. For these changes I found that the tip temperaturesvaried, in the manner indicated in the chart 32, from about 280 to 440.Similar tests on the other types of burners, described below, gavecurves quite similar to that shown in Figure 2.

Primarily, it is believed that the underlying principle, whereby thetemperature changes registered on the instrument 22 responds quiteuniformly to corresponding changes in the characteristics of the gas, isdue to the effect of said changes upon the amount of radiant heat fromthe flame absorbed by the burner tip. The amount of radiant heat that isemitted by a flame varies according to the composition of the gasburned, for with different gases different proportions of the total heatemitted appear as radiant heat, and of course with the same kind of gas,and hence a constant proportion of radiant heat, the amount of radiantheat emitted from any given flame varies as the total heat of thatflame. Now the amount of radiant heat absorbed by the burner tiptherefore varies as the above two factors, namely, composition of thegas insofar as it affects the proportion of heat emitted as radiantheat, and total heat value of the flame assuming a constant type of gas.Further, however, the amount of radiant heat absorbed by the burner tipvaries as a third factor which is flame speed. Assuming a gas having aconstant total heat value and a constant radiant heat proportion, itwill be seen that an increase in flame velocity of the gas will resultin a higher temperature at the burner even though the other factors justmentioned remain the same. That is to say, assuming such a change in thegas supplied that the flame speed of the mixture is increased, the flame3!] will occupy a position somewhat closer to the tip '1, as indicatedin dotted lines in Figure 1, and the temperature of the tip, which isthen closer to what might be termed the center of heat, that is, apointfr'om which it may be considered that all of the heat of the flameoriginates, will increase an amount approximately proportional to theincrease in flame velocity. The amount of radiant heat absorbed by anyobject, such as the tip I, is proportional to the area of that objectand the square of the distance from the radiating source, and since thearea of the burner tip is a constant and an increase in the flamevelocity will cause the center of heat of the flame to approach closerto the tip I, it therefore follows that with an increase in flamevelocity the tip will become hotter and the corresponding increasedtemperature indication will be registered on the instrument 22.

From the above-described operation, it will be apparent that the presentdevice will afford an indication of practically any change in a gaswhich affects its burning characteristics. It is particularly adapted tofurnish an indication of the flame speed of the gas, but it is notnecessarily limited thereto, since the device is just as responsive toany other change in the gas or the characteristics thereof that affectthe total amount of heat, the height or shape of the flame, or theamount of radiant heat emitted by the gas when burned. It is well knownthat different constituents of the gas give different radiatingcapacities, although the total heat evolved by any given flame would bethe same.

Heretofore, attempts have been made to provide flame analyzers butgenerally they include some form of temperature responsive devicedisposed in the flame itself. Where such a device is in the nature of athermocouple, the latter while furnishing a useful indication of thetemperature of the flame at certain points, is responsive only to anegligible degree, if at all, to the radiant heat of the flame, Further,such devices, being in the flame zone itself, interfere with the properburning of the gas and may corrode or otherwise change so that the heattransfer is affected. Also different portions of the flame are atdifferent temperatures, so that the temperature registered by thoseflame analyzers having thermocouples or other devices within the flameitself do not furnish a consistent indication which is uniformthroughout the range desired.

Another disadvantage of measuring flame temperatures directly is thatthe temperatures are quite high, sometimes reaching 3060" and due to thesmall mass of the thermocouple in the flame, it would therefore begreatly affected by drafts, gas and air temperature variations, or thelike, since the thermocouple would have practically no residual heat.Further, where such high temperatures are encountered, it would bedifficult, if not impossible, to secure uniform temperature variationsfor relatively small changes in the characteristic of the gas. Also, thethermocouples have a short life where they are maintained at hightemperatures in a reducing atmosphere, and the structural changesresulting therefrom would, in addition, affect the thermal response ofthe thermocouple. However, the present device is adapted as a flamepropagation analyzer and it provides a very uniform indication of flamespeeds and is not subject to the wide fluctuations to whichthermocouples and other ject.

If desired, instead of merely indicating the temperature at the gasburner tip, or the difference between the temperature of the gas mixturebefore combustion and the temperature of the tip, the present inventioncontemplates providing means responsive to these temperatures foreffecting the desired or required controlling operations automatically.Thus, for example, where it is desired to provide a continuous cent'rolfor, say, the amount of decelerant or the amount of carburetted watergas at 800 B. t. u. to be added to the gas supplied to the customer, theburner I would be connected as described above in connection with Figurel, with the gas supply and the other factors, such as temperatur'e,specificgravity, and composition maintained constant, the amount to beadded can be nicely controlled by the apparatus shown in Figure 3.

Referring now to Figure 3, it will be seen that the two thermocouplesI5' and I6 are connected to the burner I in substantially the samemanner described above. However, instead of being connected directly toan indicating galvanometer 22, as in Figure 1, the leads 26a and 2 laextend to a continuously operating recording and controllingpotentiometer, indicated in its entirety by the reference nuineral 35.An instrument of this char 'acter is well known to those skilled in theart and is at present available in the open market. Generally, theyconsist of a galvanometer 36 controlling an indicating hand 31, whichindicates temperature, and a recording pen 38 which recor'ds temperatureon a continuously moving record strip 39. Through suitable mechanism,the details of which per Se are of no particular concern, changes oftemperature between the tip of the burner and the inflowing gas mixtureunbalance the galvanometer circuit in the instrument 36, which sets inmotion the recording pen 38 and also a shaft 4| which at one end carriesa sliding contact 42. The contact 42 engages a slide wire 44, one end ofwhich is connected by a lead 45 to one pole of a standard cell 46arranged to supply constant voltage, the other end of the slide wire 44being connected through a lead 41, an adjustable resistance 48 and alead 49 to the other pole of the standard cell 46. As will be recognizedbythose familiar with instruments of different types, the momentaryunbalance of the galvanometer circuit, occasioned by temperature changebetween the thermocouples l5 and I6, results in a'n actuation of themechanism including the shaft 4| which, rocking the arm 42 along thewire 44, brings the galvanometer back into balance, the correspondingmovement of the shaft 4| operating the recording arm 38.

According to'the present invention, I make use of this type ofinstrument by mounting on the shaft 4| a mercury switch indicated in itsentirety by reference numeral 66. The switch 6|] includes a tube 6|containing a globule of mercury and having at each end a pair ofconstant points 63, 64 and 65, 66. The leads 64 and 65 are connected toa wire 61, and wires 68 and 69 are connected, respectively, to thecontacts 63 and 66. A first relay 1| may be connected between the wires61 and 68, and a second relay 12 may be connected between the wires 61and 69.

Thus, when the temperature at the tip of the burner increases, thiswould indicate that more decelerant would be required, and the resultingunbalance of the galvanometer circuit would cause the shaft 4| to swingin one direction thus closing oneof the pairs of contacts 63, 64 or 65,66. This would'actuate one of the relays which is connected to anycontrol apparatus desired, such a valve mechanism, for adding more de-rcelerant to the system. Conversely, if the temperature at the tip beginsto fall, the resulting unbalance of the galvanometer circuit wouldresult in the shaft 4| turning in the other direction, thereby actuatingthe other relay which can be connected to close the valve, thusdiminishing the amount of decelerant added.

The present arrangement is also admirably adapted to control thecomposition of the gas by controlling the amount of carbureted water gasto be added to the system to supplement the regular gas mixture asexplained above. Since the addition of carbureted water gas to the usualmixture may produce a different burning gas, it is particularlyimportant that the station, adding its make gas to that received fromthe main plant for distribution, know or have an indication orregistration of the amount of carbureted water gas already added to themixture which is received at the station.

The present invention is admirably adapted for use at such stationssince it is a simple matter to connect a line from the gas supply to theinlet 3 of the burner I. Then, after the gas is ignited and the burnertemperatures become stabilized, the indications on the galvanometer 22,or the controlling operations effected by the instrument 35, can be usedto prevent an inadvertent addition of excessive quantities of make gasby the stations to the gas supply received from the main source.Ordinarily, a Bunsen burner is capable of burning satisfactorily underwider conditions of gas variations than the burners of most appliances,and in operation I arrange the control mechanism of Figure 3, or causethe operation of the usual controls under the guidance of the apparatusshown in Figure 1, so that the temperatures indicated or recorded fallwithin limits that experience has shown result in a satisfactory gas fordistribution to the consumers. For example, when measuring the amount ofcarburetted gas that has been added, as indicated in the chart of Figure2, the point a should not be exceeded, since generally no more thanaround 55% of carburetted water was at 800 B. t. u. should be added tobase gas at 800 B. t. u. This may of course vary, depending onconditions an other factors.

The control apparatus shown in Figure 3 may .be used to govern suchother factors as gas-air proportioning, pressure and the like. Forexample, the controlling apparatus shown in Figure 3 may be arranged tocontrol flame height, that is, height of the inner cone. In someindustrial installations, such as automatic can forming machines, it isvery essential to have the inner cone maintained at a constant height,and by the use of the present invention the potentiometer shaft 4! maybe connected to any suitable controlling means, such as through therelays H and 12, to control the gas-air proportion to maintain theheight of the inner cone constant. This may be done by connecting therelays H and 12 to some form of motor device for determining the amountof air added. Also, the control apparatus of the present invention canbe arranged to control the pressure at which the gas supply is deliveredto the customers mains or appliances. Heretofore, relatively elaborateapparatus is required to maintain the pressure constant, but accordingto the present invention, it would be necessary merely to connect therelays H and 12 to some form of motor valve. Thus, a change intemperature at the burner tip would result in unbalancing thegalvanometer circuit momentarily which, as described, would energize oractuate one or the other of the relays to secure a readjustment of themotor valve.

It will be obvious, of course, that forms of controlling means otherthan that shown in Figure 2 may be incorporated with the test or controlburner, and likewise various forms of burners may be employed incarrying out the principles of my invention. For example, in Figure 4 Ihave shown a more or less conventional Bunsen burner H! having a gasinlet ll and an adjustable sleeve 12 having one or more primary airinlets I3, being substantially the construction indicated in Figure 1. Athermocouple I6 is arranged within the burner tube just above the inletfor the gas and the primary air, and the hot thermocouple I5 isconnected to a screen 11 supported in any suitable manner above the endof the burner tube in such a manner that the screen becomes the tip ofthe burner, since each small opening in the screen has its own flamecone. The thermocouples l5 and I6 are connected difierentially by leadsI9, 20, and 2|, either to an indicating galvanometer such as the oneindicated at 42 in Figure 1, or a recording or control apparatus such asthat shown at 35 in Figure 3.

The construction indicated in Figure 4 has slightly different operatingcharacteristics as compared with the type of burner shown in Figure 1having the tip I and an insulated sleeve In. In Figure 4, the screen 11is especially responsive to changes in the flame characteristics and isinsulated from the burner tube by an air space indicated at 83.

As mentioned above in connection with Figure 1, some form of insulationis usually provided between the burner tip, that is, that part whosetemperature responds to flame conditions which, in turn, is responsiveto various characteristics of the gas-air mixture being burned. Theinsulation is desired in order that there should not be too great a flowof heat from the tip end of the burner to the other portions andparticularly from the main body of the tip to the surroundingatmosphere. Figure 5 illustrates a construction in which theconventional Bunsen burner 10 is employed and the thermocouples l5 andI6 connected, respectively, to the tip end of the burner tube andadjacent the lower end as in the previously described constructions. Inorder to prevent too great a heat loss from the burner tube to thesurrounding atmosphere, the construction shown in Figure 5 embodies asleeve 86 that surrounds the tube 85 and is formed of insulatingmaterial of any suitable kind which is satisfactory at the temperatureencountered. The insulating sleeve is held in place by a cap screw 81and extends up to a short distance from the tip end of the tube 85. Theamount of the tube exposed determines the portion of the tube thatreceives heat from the flame and therefore the position of the sleevedetermines to some extent the range of temperatures which any givenchange in the gas will cause. The thermocouples I5 and [6 are connecteddifferentially in the same manner shown in Figures 1 and 3. As will beapparent, the sleeve 86 may be adjusted vertically to vary the area ofthe burner tip exposed to the heat of the flame.

Under other conditions it may be desirable to provide the test orcontrol burner with means for dissipating heat from the burner tip,rather than insulating means or other mechanism for lessening the heatflow away from the burner tip to which the thermocouple is connected.Figures 6 and 7 illustrate an arrangement of this kind in which theburner carries a screen heat dissipator 90. Preferably the screen 90 isin the form of a sleeve or cylinder having a number of convolutions, theinner portion of which are secured in any suitable manner to the end ofthe burner tube. While the primary purpose of the sleeve 90 is todissipate heat from the tip of the burner, it will be observed,particularly from Figure '7, that there is, nevertheless, a fairlysubstantial area of material exposed to the radiant heat emitted fromthe flame, and therefore the burner shown in Figures 6 and '7' readilyresponds to changes in the amount of radiant heat in the flame.

Figure 8 shows a slightly different form of burner but one which, forall practical purposes, is quite similar to the type of burner shown inFigure l. A tip 95 is provided with a flared portion 95 which encirclesthe upper end of the burner tube 91 and is carried thereby through themedium of small pins 98 or the like. This construction prevents toogreat a heat flow from the tip 95 down to the burner tube 91. However,the tip sleeve 95 has sufficient area disposed to the flame so as to beresponsive to a large degree to the amount of radiant heat emitted bythe flame.

Under, other conditions it may be desirable to provide a burner which isespecially adapted to respond to radiant heat, and, as shown in Figure9, to this end I provide the burner 10 with a flat disc or auxiliaryring lfll secured by welding or'the like to the tip end of the burner soas to present a relatively great area to pick up the radiant heat raysemitted by the flame. The thermocouples l5 and l6in the form of theinvention shown in Figure 9 are connected in the usual manner. Ifdesired, however, the thermocouple I5 may be secured to the ring l0]. Toa certain extent the disc [0| also acts to dissipate heat from theburner tube, and therefore the gas but each has its own' range oftemperatures. However it was found in all cases that temperature changesfollowed a definite well defined curve for changes in gas mixtures, andthat the curve shown in Figure 2 is representative of the response ofburner temperatures to changes in flame characteristics.

If desired, any of the above described burners may be equipped with ashield surrounding the same with air inlets at the lower end and theshield extending upwardly far enough to inclose the flame and preventthe latter from being affected by drafts or currents of air in thesurrounding atmosphere. Such a shield is indicated in Figure 3 by thereference numeral H0 and includes a shell III carried by the base of theburner, or by any other suitable means; and which has one or more inletopenings H2 to pro vide for a flow of air to the .primary air inlets 26.Preferably, the shield extends upwardly beyond the flame, and as will beclear, a shield may be and preferably is provided for each of theburners shown in the other figures.

From the above description it will therefore be apparent that, accordingto the present invention, simple but accurate means is provided forascertaining changes in the characteristics of the gas by measuringtemperature changes at a given point on the burner, the temperature atwhich given point varies as follows:

As the flame velocity of the particular gas mixture varies, since anincrease in the flame velocity, other factors remaining the same, willcause the flame, in effect, to burn closer to the tip where thetemperature measurements are made;

As the heating value of the gas, since the hotter the flame the greaterwill be the temperature at the tip of the burner, other factorsremaining the same; and

As the constituents of the gas, especially those which affect theradiant heat emitted from the flame, which may vary even though thetotal heat value of the flame might remain constant.

What I claim, therefore, and desire to secure by Letters Patent is:

1. Apparatus for comparing combustion characteristics of differentcombustible gases and mixtures thereof comprising a burner tube havingair and gas inlet means, a pair of differentially connectedthermocouples, one being disposed Within the tube adjacent said inletmeans and the other being disposed on the tube adjacent its outer end soas to measure the temperature rise of said outer end of said tube dueonly to the combustion of air and gas by the burner, and a temperaturemodifying sleeve surrounding said tube between said thermocouples.

2. Apparatus for comparing combustion characteristics of differentcombustible gases and mixtures thereof comprising a burner tube havingair and gas inlet means, a pair of differentially connectedthermocouples, one being disposed within the tube adjacent said inletmeans and the other being disposed on the tube adjacent its outer end soas to measure the temperature rise of said outer end of said tube dueonly to the combustion of air and gas by the burner, and a heatinsulating sleeve surrounding said burner tube for a substantial portionof its length, a portion of said tube to which said other thermocoupleis connected being exposed beyond the outer end of said insulatingsleeve.

3. Apparatus for comparing combustion characteristics of differentcombustible gases and mixtures thereof comprising a burner tube havingair and gas inlet means, a pair of differentially connectedthermocouples, one being disposed within the tube adjacent said inletmeans and the other being disposed on the tube adjacent its outer end soas to measure the temperature rise of said outer end of said tube dueonly to the combustion of air and gas by the burner, and a sleeve ofscreen-like material having ex-- tensive superficial area and secured inheat transmitting relation to the outer end of said tube for radiatingheat therefrom.

4. Apparatus for comparing combustion characteristics of differentcombustible gases and mixtures thereof comprising a burner tube havingair and gas inlets, a plurality of pins carried at the upper end of saidtube, a short sleeve supported on said pins in insulated relation withrespect to said tube, and a pair of differentially connectedthermocouples, one fixed to said sleeve and the other disposed withinsaid burner tube adjacent said inlets so as to measure the temperaturerise of said sleeve due only to the combustion of air and gas by theburner.

5. Apparatus for comparing combustion characteristics of differentcombustible fluids and mixtures thereof comprising, a burner including atube through which the combustible fluid flows to a flame at one end,metallic means at the base of the flame eflectively heat insulated fromthe other end of said tube, and means for measuring the temperature riseof said metallic means due only to heat from said flame.

6. Apparatus for comparing combustion characteristics of difierentcombustible fluids and mixtures thereof comprising, a burner including atube through which the combustible fluid flows to a flame at one end,metallic means at the base of the flame, means effectively heatinsulating said metallic means from the other end of said tube so thatheat received by said metallic means from said flame is concentratedthereat, and means for measuring the temperature rise of said metallicmeans due only to heat from said flame.

7. Method of determining where to stop in adding a supplementarycombustible gas to a base combustible gas having different combustioncharacteristics than the supplementary gas for supplying burnersadjusted to operate satisfactorily using the base gas which comprises:measuring the diflerence between the temperature of a mixture of thecomposite gas and air in a burner as it flows to a flame and thetemperature of a part of the burner exposed to the heat of the flame.

MATHEW G. MARKLE.

